The objective of this proposal is to develop a novel technology for parallel synthesis of RNA microarray on solid surfaces (RNA-chips). Although DNA-chips have emerged as a high efficient and comprehensive tool for cancer gene analysis, drug discovery and a variety of bioassays, a parallel development of RNA-chips has not been possible, primarily because there is no practical method that can achieve efficient and economic parallel synthesis of RNA microarrays. In this proposal, a method of RNA-chip synthesis using novel photochemical reactions in combination with conventional chemistry of RNA synthesis will be developed. The method uses photogenerated reagents to allow optical control of a single reaction step, such as deprotection of blocking groups, in a sequence of reactions. Using a microarray reactor and a programmable digital optical projector, parallel synthesis of thousands of diverse RNA sequences can be achieved with high efficiency and low costs. Our Phase I goals are to obtain prototype RNA oligonucleotide arrays using the proposed method of light directed parallel synthesis and demonstrate hybridization patterns of the RNA-chips synthesized. A novel combinatory strategy using our chip technology will be applied to screen hundreds of photoreaction conditions. New applications of the light controlled RNA-chip synthesis will be explored. Our Phase II goals are to produce next generation of high quality RNA-chips containing oligonucleotides composed of 20-40 residues and establish the applications of RNA cancer gene-chips and RNA library-chips in identification of RNA targets by antisense oligonucleotides and potential antitumor agents. RNA-chips provide unambiguous sequence information and are indispensable and powerful tool for direct investigation of RNA interactions with a variety of ligand molecules in cancer analysis and drug development and in the study of many human diseases. It is expected that in keeping pace with rapidly mounting information in RNA genomics, there will be an escalated effort in identifying RNA sequences as specific diagnose and therapeutic targets. Our proposed research is to provide a highly efficient, flexible and easily accessible technology to accelerate these discovery processes.